oBGP: An Overlay for a Scalable iBGP Control Plane

The Internet is organized as a collection of networks called Autonomous Systems (ASes). The Border Gateway Protocol (BGP) is the glue that connects these administrative domains. Communication is thus possible between users worldwide and each network is responsible of sharing reachability information to peers through BGP. Protocol extensions are periodically added because the intended use and design of BGP no longer fit the current demands. Scalability concerns make the required iBGP full mesh difficult to achieve in today’s large networks and therefore network operators resort to confederations or Route Reflectors (RRs) to achieve full connectivity. These two options come with a set of flaws of their own such as persistent routing oscillations, deflections, forwarding loops etc. In this paper we propose a new architecture for the redistribution of external routes inside an AS. Instead of relying on the usual statically configured set of iBGP sessions, we propose to use an overlay of routing instances that are collectively responsible for (i) the exchange of routes with other ASes, (ii) the storage of internal and external routes, (iii) the storage of the entire routing policy configuration of the AS and (iv) the computation and redistribution of the best routes towards Internet destinations to each router of the AS.